Category: Science

Quantum fluctuations stabilize high-temperature superconductors

Supercomputers are indispensable in the research of superconductors, materials in which electricity flows without loss. Using simulations on CSCS supercomputer ‘Piz Daint’, an international team of researchers has now shown that physics has not been sufficiently considered in the study of superconductors made of so-called hydrides. February 6, 2020 – by Simone Ulmer  (This post …

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Our most recent article is published in Nature!

Together with collaborators in Spain (Prof. Errea and his team), Italy (Prof. Mauri and his team), France (Prof. Calandra), Germany (Dr Sanna), and Japan (Prof. Arita, Prof. Koretsune and Prof. Tadano) we have shown, in our most recent publication that the crystal structure of the record superconducting LaH10 compound is stabilised by nuclear quantum fluctuations. …

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Enhancing transparent copper iodide, available dopants?

In our most recent work, the zinc blende phase of copper iodide (CuI) was investigated using a computational high-throughput approach. This material notably holds the record hole conductivity for intrinsic transparent p-type semiconductor. In our study, eight impurities suitable for n-type doping were discovered. Unfortunately, the work reveals that donor doping is hindered by compensating …

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Review on high-Tc superconductors: Methods and Materials

I am very excited to finally release my latest work that has been running on parallel for more than a year. Notably, the last five months have been of an intense, insane amount of work. The number of hours invested in this work has been many more from the initially planned. I wish to thank …

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New playground materials: Magnetic nitrides Perovskites

We propose a novel class of materials: stable nitrides with a perovskite-type structure and magnetic rare-earth metals. These materials are thermodynamically stable and, despite possessing the different atomic environments, retain the magnetic moment of their guest, the rare-earth metal.  We find both magnetic metals and insulators, with a variable range of magnetic moments and some …

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Revealing unexplored dopants in semiconducting materials

The advancement of transparent electronics, one of the most anticipated technological developments for the future, is currently inhibited by a shortage of high-performance p-type conductors. In materials, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical and optical and structural properties. Recent demonstration of tin monoxide as …

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Emergence of Perovskite (MAPI) phases upon little compression

Perovskites are among the most promising and versatile class of candidate compounds for new or improved materials in energy applications, including photovoltaics, superconductivity, and lasing. With the general formula ABX3, the perovskite structure consists of corner-sharing BX6 octahedra forming a three-dimensional (3D) framework that provides room for the A units in the resulting cuboctahedral cavities. …

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Not all materials are metallic under pressure: tuning the gap !

Highly stable materials are usually wide-gap insulators, where covalency dominates the ionic exchange, such as in carbon (diamond), MgO, and LiH, to name a few.  In our latest work,  in collaboration with experimental teams in USA,  UK, and Japan we studied the enhanced stability of Sn3N4 to applied pressure and temperature. Our predicted phase transitions were confirmed by state-of-the-art Synchrotron X-ray diffraction and …

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Possible superconductivity in hydrogenated carbon nanostructures

In this work we present an application of density-functional theory for superconductors (SCDFT) to superconductivity in hydrogenated carbon nanotubes and fullerane (hydrogenated fullerene). We show that these systems are chemically similar to graphane (hydrogenated graphene) and like graphane, upon hole doping, develop a strong electron phonon coupling. This could lead to superconducting states with critical …

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Doping polyethylene, the next superconductor?

High pressure is an exciting field that has evolved incredibly far since the pioneering work of Cailletet, Amagat and Bridgman. A substantial amount of research in the field of high pressure (post-Bridgman era) was triggered by the tantalizing idea of metalizing hydrogen (Wigner and Huntington transition) which dates back to the mid 30’s. The metalization …

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“Cold-Passivation” of Defects in Tin-Based Oxides

Our latest results arising from a collaborative work with experimental groups in École Polytechnique Fédérale de Lausanne (EPFL), Neuchâtel,  University of California Berkeley, National Institute of Advanced Industrial Science and Technology (AIST Japan) and the Institute for Nanotechnology, University of Twente, is published now in Journal of Physical Chemistry C  (link). In this work we …

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Crystal defects for qubits

We had the opportunity to attend the CECAM-Workshop “Crystal defects for qubits, single photon emitters and nanosensors” in Bremen (Germany), an interesting and forefront workshop in crystal defects for quibits. Since we all know, the leading contender is the nitrogen-vacancy center in diamond which may be considered as a robust quantum tool. Several quantum algorithms and …

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Structures of exohedrally decorated C60-Fullerenes

In our most recent publication we studied the exohedrally metal decorated carbon-fullerenes. These systems are a promising material for its good hydrogen adsorption (high concentrations and with optimal binding energies) properties. Since their geometry and type of coverage play a key role in determining the H2 adsorption mechanism, in this paper just accepted in Carbon …

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Searching hole-electron substitutional dopants for TCO technologies

The combination of optical transparency and high electrical conductivity enables transparent conductive oxide (TCO) materials to be used for a wide range of applications -from simple smart window coatings to OLEDs and futuristic see-through displays.  Doped tin-dioxide (SnO2) is an important semiconductor that is already used for these applications. However, in order to uncover the …

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Resolving the open controversies on the anomalous #superconducting trends in metastable phases of #Phosphorus

Among elemental compounds, the high-pressure superconducting phase diagram of phosphorus is one of the most complex. In this work, we measured electrical resistivity and performed ab initio superconductivity calculations in order to solve, for the first time the open controversies on the anomalous superconducting trends. Our work forms on a single picture a consistent scenario …

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Layered binaries as candidates for hard-magnets

For the most recent work on hard-magnetic systems we focused in binaries stacked layers of FePt, MnAl and MnGa. In this work an enhancement of the  mangetocrystalline  anisotropy was calculated for specially stacked structures. After a long search and great effort of the wonderful team of collaborators (special thanks and all the credit goes to …

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Piz Daint 3rd fastest supercomputer

The supercomputer ranking published on 19 June 2017, places Switzerland’s 19.6 petaflop Piz Daint supercomputer third in the world after Sunway TaihuLight and Tianhe 2, two Chinese supercomputers. Piz Daint’s recent upgrades allowed it to climb five positions up the ranking. With a performance of 93 petaflops, China’s TaihuLight is by far the most powerful number-cruncher …

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Cornell 2017: Hoffmann, Ashcroft, Mermin

During my days in Ithaca (Cornell University), I had the great opportunity to show part of my research work. I decided to present the research I had just finished at that time about the possibility to induce a metallic state in ice under pressure and upon doping; thinking that I could attract more attention and …

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The elephant in the room of density-functional theory calculations

While basis set convergence sounds straightforward (though time-consuming) it is hard to rule out that underlying assumptions in  the design of the basis set influences the results.  However, converged basis set DFT results are needed to separate basis set errors from errors due to the functional. Multiwavelets, a systematic and adaptive multiresolution numerical solution of the …

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H2O ice as superconductor? yes, superconducting water !

We have recently investigated the possibility of achieve high-temperature superconductivity in hydrides under pressure by inducing metallization of otherwise insulating phases through doping, a path previously used to render standard semiconductors superconducting at ambient pressure. Following this idea, we study HO, which is one of the most abundant and well-studied substances in the universe! We …

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